Changes In Density And Localization Of Glut1 And Mct1 Transporters Of Cancer Cells Induced By Ketones

Ketone supplementation has been investigated as a potential therapy and/or as adjuvant with traditional cancer treatments. Previous studies have indicated that ketone supplementation decreases viability and proliferation of cultured tumor cells, as well as prolongs survival of mice with metastatic cancer. The primary fuel for cancer cells is glucose that enters the cells through glucose transporters (GLUT), while lactate, another key energy source for cancer cells that has been shown to enhance tumor angiogenesis, is exported through monocarboxylate transmembrane transporters (MCT). The inhibition of these transporters could lead to promising anti-cancer therapies, therefore, we investigated the changes in the density and localization of GLUT1 and MCT1 transporters in various cancer cell lines in response to R,S-sodium-3-hydroxybutyrate (βHB) in the culture media, in order to identify underlying mechanisms of the previously observed anti-cancer effects. We studied mice metastatic cancer (VM-M3), human brain cancer (U87MG) and human lung cancer (A549) cells using indirect immunofluorescence assay with microplate photometer and confocal microscopy. Cells were cultured in 12 or 96-well plates, and after 2 days they were treated with graded concentrations of βHB for 24 hrs, followed by immunofluorescent reaction. In VM-M3 cells only 1 nM βHB treatment decreased GLUT1 density, but not higher concentrations. A statistically significant decrease in GLUT1 density was detected with increasing βHB concentration starting at 2 nM in U87 cells and at 5nM in A549 cells. The density of MCT1 transporter decreased in all cell types with βHB treatment, and less protein was localized in the cell nucleus. These results suggest a possible mechanism for ketone bodies to decrease cancer cell viability via decreased ability to take up glucose and export lactate. However, the lowest effective concentration was different in each cell type and it is possible that higher concentrations might induce compensatory mechanisms. Further exploration of the effects of ketones on the expression of cell surface proteins and transporters relevant to cancer cell metabolism may improve our understanding of the clinical relevance of ketone supplementation in the treatment of cancer.